Field
The present invention relates to a connecting rod for an internal combustion engine.
Description of the Related Art
In an internal combustion engine, a connecting rod connects a piston pin to a crankpin so that the reciprocating motion of the piston along the axis of the cylinder is converted to the rotating motion of the crankshaft. The connecting rod has a small-diameter connecting hole formed in one end for connection to the piston pin, and a large-diameter connecting hole formed in the other end for connection to the crankpin.
During operation of the internal combustion engine, a large load acts from an edge of the connecting hole of the connecting rod on a power transmitting pin such as the piston pin, the crankpin or the like. Therefore, a connecting rod devised for improvement in wear resistance property of the power transmitting pin is formed such that the inner peripheral face of a base-material hole of connecting-rod base material is covered with a coating material softer than the connecting-rod base material by plating or the like in order to form a connecting hole (for example, see JP-A No. 2001-511500 (Patent Literature 1)).
In the above-described connecting rod of the related art, when a large load acts on the power transmitting pin from the edge of the connecting hole, the soft coating material applied to the connecting hole is elastically deformed, thereby reducing the contact pressure acting on the power transmitting pin from the edge of the connecting hole.
As the engine operating speed is increased in an internal combustion engine, the power transmitting pin bends, so that the axial end of the power transmitting pin is strongly pressed against a portion around the axially outer end of the connecting hole of the connecting rod.
However, in the above-described connecting rod in the related art, the constant-inner-diameter inner-peripheral face of the base-material hole forming part of the connecting hole is uniformly coated with the coating material. Because of this, it is difficult to reduce with efficiency the constant pressure exerted on a portion of the power transmitting pin coming into contact with a portion around the axially outer end of the connecting hole.